It's the Barbie bus patch

Message-ID: <20060110054243.GA26165@petdance.com>

p4raw-id: //depot/perl@26764

21 files changed, 260 insertions, 298 deletions

diff --git a/av.c b/av.c
index 42e1887a31..19aeffbd30 100644
--- a/av.c
+++ b/av.c
@@ -367,7 +367,7 @@ Perl_newAV(pTHX)
     sv_upgrade((SV *)av, SVt_PVAV);
     /* sv_upgrade does AvREAL_only()  */
     AvALLOC(av) = 0;
-    SvPV_set(av, (char*)0);
+    SvPV_set(av, NULL);
     AvMAX(av) = AvFILLp(av) = -1;
     return av;
 }
@@ -482,7 +482,7 @@ Perl_av_undef(pTHX_ register AV *av)
     }
     Safefree(AvALLOC(av));
     AvALLOC(av) = 0;
-    SvPV_set(av, (char*)0);
+    SvPV_set(av, NULL);
     AvMAX(av) = AvFILLp(av) = -1;
 }
 
diff --git a/doio.c b/doio.c
index 1dc4169beb..84744658f2 100644
--- a/doio.c
+++ b/doio.c
@@ -1381,7 +1381,7 @@ Perl_do_aexec5(pTHX_ SV *really, register SV **mark, register SV **sp,
 #else
     if (sp > mark) {
 	char **a;
-	const char *tmps = Nullch;
+	const char *tmps = NULL;
 	Newx(PL_Argv, sp - mark + 1, char*);
 	a = PL_Argv;
 
@@ -1391,7 +1391,7 @@ Perl_do_aexec5(pTHX_ SV *really, register SV **mark, register SV **sp,
 	    else
 		*a++ = "";
 	}
-	*a = Nullch;
+	*a = NULL;
 	if (really)
 	    tmps = SvPV_nolen_const(really);
 	if ((!really && *PL_Argv[0] != '/') ||
@@ -1544,7 +1544,7 @@ Perl_do_exec3(pTHX_ const char *incmd, int fd, int do_report)
 	if (*s)
 	    *s++ = '\0';
     }
-    *a = Nullch;
+    *a = NULL;
     if (PL_Argv[0]) {
 	PERL_FPU_PRE_EXEC
 	PerlProc_execvp(PL_Argv[0],PL_Argv);
@@ -1553,15 +1553,13 @@ Perl_do_exec3(pTHX_ const char *incmd, int fd, int do_report)
 	    do_execfree();
 	    goto doshell;
 	}
-	{
-	    if (ckWARN(WARN_EXEC))
-		Perl_warner(aTHX_ packWARN(WARN_EXEC), "Can't exec \"%s\": %s",
-		    PL_Argv[0], Strerror(errno));
-	    if (do_report) {
-		const int e = errno;
-		PerlLIO_write(fd, (void*)&e, sizeof(int));
-		PerlLIO_close(fd);
-	    }
+	if (ckWARN(WARN_EXEC))
+	    Perl_warner(aTHX_ packWARN(WARN_EXEC), "Can't exec \"%s\": %s",
+		PL_Argv[0], Strerror(errno));
+	if (do_report) {
+	    const int e = errno;
+	    PerlLIO_write(fd, (const void*)&e, sizeof(int));
+	    PerlLIO_close(fd);
 	}
     }
     do_execfree();
diff --git a/embed.fnc b/embed.fnc
index b54969d3cb..dfe412daa1 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -1278,7 +1278,6 @@ ERs	|bool	|reginclass	|NN const regnode *n|NN const U8 *p|NULLOK STRLEN *lenp\
 				|bool do_utf8sv_is_utf8
 Es	|CHECKPOINT|regcppush	|I32 parenfloor
 Es	|char*|regcppop
-Es	|char*|regcp_set_to	|I32 ss
 Es	|void	|cache_re	|NN regexp *prog
 ERs	|U8*	|reghop		|NN U8 *pos|I32 off
 ERs	|U8*	|reghop3	|NN U8 *pos|I32 off|NN U8 *lim
diff --git a/embed.h b/embed.h
index f359500745..88804deb60 100644
--- a/embed.h
+++ b/embed.h
@@ -1303,7 +1303,6 @@
 #define reginclass		S_reginclass
 #define regcppush		S_regcppush
 #define regcppop		S_regcppop
-#define regcp_set_to		S_regcp_set_to
 #define cache_re		S_cache_re
 #define reghop			S_reghop
 #define reghop3			S_reghop3
@@ -3343,7 +3342,6 @@
 #define reginclass(a,b,c,d)	S_reginclass(aTHX_ a,b,c,d)
 #define regcppush(a)		S_regcppush(aTHX_ a)
 #define regcppop()		S_regcppop(aTHX)
-#define regcp_set_to(a)		S_regcp_set_to(aTHX_ a)
 #define cache_re(a)		S_cache_re(aTHX_ a)
 #define reghop(a,b)		S_reghop(aTHX_ a,b)
 #define reghop3(a,b,c)		S_reghop3(aTHX_ a,b,c)
diff --git a/gv.c b/gv.c
index 42c15561f3..7ebf28030e 100644
--- a/gv.c
+++ b/gv.c
@@ -435,20 +435,20 @@ Perl_gv_fetchmeth_autoload(pTHX_ HV *stash, const char *name, STRLEN len, I32 le
 	GV **gvp;
 
 	if (!stash)
-	    return Nullgv;	/* UNIVERSAL::AUTOLOAD could cause trouble */
+	    return NULL;	/* UNIVERSAL::AUTOLOAD could cause trouble */
 	if (len == S_autolen && strnEQ(name, S_autoload, S_autolen))
-	    return Nullgv;
+	    return NULL;
 	if (!(gv = gv_fetchmeth(stash, S_autoload, S_autolen, FALSE)))
-	    return Nullgv;
+	    return NULL;
 	cv = GvCV(gv);
 	if (!(CvROOT(cv) || CvXSUB(cv)))
-	    return Nullgv;
+	    return NULL;
 	/* Have an autoload */
 	if (level < 0)	/* Cannot do without a stub */
 	    gv_fetchmeth(stash, name, len, 0);
 	gvp = (GV**)hv_fetch(stash, name, len, (level >= 0));
 	if (!gvp)
-	    return Nullgv;
+	    return NULL;
 	return *gvp;
     }
     return gv;
@@ -1458,9 +1458,9 @@ Perl_Gv_AMupdate(pTHX_ HV *stash)
     for (i = 1; i < lim; i++)
 	amt.table[i] = Nullcv;
     for (; i < NofAMmeth; i++) {
-	const char *cooky = PL_AMG_names[i];
+	const char * const cooky = PL_AMG_names[i];
 	/* Human-readable form, for debugging: */
-	const char *cp = (i >= DESTROY_amg ? cooky : AMG_id2name(i));
+	const char * const cp = (i >= DESTROY_amg ? cooky : AMG_id2name(i));
 	const STRLEN l = strlen(cooky);
 
 	DEBUG_o( Perl_deb(aTHX_ "Checking overloading of \"%s\" in package \"%.256s\"\n",
@@ -1484,7 +1484,7 @@ Perl_Gv_AMupdate(pTHX_ HV *stash)
 		/* This is a hack to support autoloading..., while
 		   knowing *which* methods were declared as overloaded. */
 		/* GvSV contains the name of the method. */
-		GV *ngv = Nullgv;
+		GV *ngv = NULL;
 		SV *gvsv = GvSV(gv);
 
 		DEBUG_o( Perl_deb(aTHX_ "Resolving method \"%"SVf256\
diff --git a/hv.c b/hv.c
index 69bbdcff68..f12f117d99 100644
--- a/hv.c
+++ b/hv.c
@@ -447,8 +447,7 @@ S_hv_fetch_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
 
     xhv = (XPVHV*)SvANY(hv);
     if (SvMAGICAL(hv)) {
-	if (SvRMAGICAL(hv) && !(action & (HV_FETCH_ISSTORE|HV_FETCH_ISEXISTS)))
-	  {
+	if (SvRMAGICAL(hv) && !(action & (HV_FETCH_ISSTORE|HV_FETCH_ISEXISTS))) {
 	    if (mg_find((SV*)hv, PERL_MAGIC_tied) || SvGMAGICAL((SV*)hv)) {
 		sv = sv_newmortal();
 
@@ -553,7 +552,7 @@ S_hv_fetch_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
 		/* Will need to free this, so set FREEKEY flag.  */
 		key = savepvn(key,klen);
 		key = (const char*)strupr((char*)key);
-		is_utf8 = 0;
+		is_utf8 = FALSE;
 		hash = 0;
 		keysv = 0;
 
@@ -596,7 +595,7 @@ S_hv_fetch_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
 		    /* Will need to free this, so set FREEKEY flag.  */
 		    key = savepvn(key,klen);
 		    key = (const char*)strupr((char*)key);
-		    is_utf8 = 0;
+		    is_utf8 = FALSE;
 		    hash = 0;
 		    keysv = 0;
 
@@ -696,7 +695,7 @@ S_hv_fetch_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
 		    /* Need to swap the key we have for a key with the flags we
 		       need. As keys are shared we can't just write to the
 		       flag, so we share the new one, unshare the old one.  */
-		    HEK *new_hek = share_hek_flags(key, klen, hash,
+		    HEK * const new_hek = share_hek_flags(key, klen, hash,
 						   masked_flags);
 		    unshare_hek (HeKEY_hek(entry));
 		    HeKEY_hek(entry) = new_hek;
@@ -920,13 +919,14 @@ SV *
 Perl_hv_delete(pTHX_ HV *hv, const char *key, I32 klen_i32, I32 flags)
 {
     STRLEN klen;
-    int k_flags = 0;
+    int k_flags;
 
     if (klen_i32 < 0) {
 	klen = -klen_i32;
-	k_flags |= HVhek_UTF8;
+	k_flags = HVhek_UTF8;
     } else {
 	klen = klen_i32;
+	k_flags = 0;
     }
     return hv_delete_common(hv, NULL, key, klen, k_flags, flags, 0);
 }
@@ -958,7 +958,6 @@ S_hv_delete_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
     register HE *entry;
     register HE **oentry;
     HE *const *first_entry;
-    SV *sv;
     bool is_utf8;
     int masked_flags;
 
@@ -981,6 +980,7 @@ S_hv_delete_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
 	hv_magic_check (hv, &needs_copy, &needs_store);
 
 	if (needs_copy) {
+	    SV *sv;
 	    entry = hv_fetch_common(hv, keysv, key, klen,
 				    k_flags & ~HVhek_FREEKEY, HV_FETCH_LVALUE,
 				    Nullsv, hash);
@@ -1051,6 +1051,7 @@ S_hv_delete_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
     first_entry = oentry = &(HvARRAY(hv))[hash & (I32) HvMAX(hv)];
     entry = *oentry;
     for (; entry; oentry = &HeNEXT(entry), entry = *oentry) {
+	SV *sv;
 	if (HeHASH(entry) != hash)		/* strings can't be equal */
 	    continue;
 	if (HeKLEN(entry) != (I32)klen)
@@ -1067,13 +1068,12 @@ S_hv_delete_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
 	}
 
 	/* if placeholder is here, it's already been deleted.... */
-	if (HeVAL(entry) == &PL_sv_placeholder)
-	{
-	  if (k_flags & HVhek_FREEKEY)
-            Safefree(key);
-	  return Nullsv;
+	if (HeVAL(entry) == &PL_sv_placeholder) {
+	    if (k_flags & HVhek_FREEKEY)
+		Safefree(key);
+	    return NULL;
 	}
-	else if (SvREADONLY(hv) && HeVAL(entry) && SvREADONLY(HeVAL(entry))) {
+	if (SvREADONLY(hv) && HeVAL(entry) && SvREADONLY(HeVAL(entry))) {
 	    S_hv_notallowed(aTHX_ k_flags, key, klen,
 			    "Attempt to delete readonly key '%"SVf"' from"
 			    " a restricted hash");
@@ -1368,8 +1368,9 @@ Perl_hv_ksplit(pTHX_ HV *hv, IV newmax)
 	if (!*aep)				/* non-existent */
 	    continue;
 	for (oentry = aep, entry = *aep; entry; entry = *oentry) {
-	    register I32 j;
-	    if ((j = (HeHASH(entry) & newsize)) != i) {
+	    register I32 j = (HeHASH(entry) & newsize);
+
+	    if (j != i) {
 		j -= i;
 		*oentry = HeNEXT(entry);
 		if (!(HeNEXT(entry) = aep[j]))
@@ -1433,7 +1434,7 @@ Perl_newHVhv(pTHX_ HV *ohv)
 
 	/* In each bucket... */
 	for (i = 0; i <= hv_max; i++) {
-	    HE *prev = NULL, *ent = NULL;
+	    HE *prev = NULL;
 	    HE *oent = oents[i];
 
 	    if (!oent) {
@@ -1447,8 +1448,8 @@ Perl_newHVhv(pTHX_ HV *ohv)
 		const char * const key = HeKEY(oent);
 		const STRLEN len = HeKLEN(oent);
 		const int flags  = HeKFLAGS(oent);
+		HE * const ent   = new_HE();
 
-		ent = new_HE();
 		HeVAL(ent)     = newSVsv(HeVAL(oent));
 		HeKEY_hek(ent)
                     = shared ? share_hek_flags(key, len, hash, flags)
@@ -1557,7 +1558,7 @@ Perl_hv_clear(pTHX_ HV *hv)
 		/* not already placeholder */
 		if (HeVAL(entry) != &PL_sv_placeholder) {
 		    if (HeVAL(entry) && SvREADONLY(HeVAL(entry))) {
-			SV* keysv = hv_iterkeysv(entry);
+			SV* const keysv = hv_iterkeysv(entry);
 			Perl_croak(aTHX_
 	"Attempt to delete readonly key '%"SVf"' from a restricted hash",
 				   keysv);
@@ -1615,7 +1616,7 @@ Perl_hv_clear_placeholders(pTHX_ HV *hv)
     i = HvMAX(hv);
     do {
 	/* Loop down the linked list heads  */
-	bool first = 1;
+	bool first = TRUE;
 	HE **oentry = &(HvARRAY(hv))[i];
 	HE *entry;
 
@@ -1639,7 +1640,7 @@ Perl_hv_clear_placeholders(pTHX_ HV *hv)
 		}
 	    } else {
 		oentry = &HeNEXT(entry);
-		first = 0;
+		first = FALSE;
 	    }
 	}
     } while (--i >= 0);
@@ -1680,7 +1681,7 @@ S_hfreeentries(pTHX_ HV *hv)
 	/* This is the one we're going to try to empty.  First time round
 	   it's the original array.  (Hopefully there will only be 1 time
 	   round) */
-	HE **array = HvARRAY(hv);
+	HE ** const array = HvARRAY(hv);
 	I32 i = HvMAX(hv);
 
 	/* Because we have taken xhv_name out, the only allocated pointer
@@ -1770,7 +1771,7 @@ S_hfreeentries(pTHX_ HV *hv)
 	if (--attempts == 0) {
 	    Perl_die(aTHX_ "panic: hfreeentries failed to free hash - something is repeatedly re-creating entries");
 	}
-    };
+    }
 	
     HvARRAY(hv) = orig_array;
 
@@ -1866,7 +1867,7 @@ Perl_hv_iterinit(pTHX_ HV *hv)
 	Perl_croak(aTHX_ "Bad hash");
 
     if (SvOOK(hv)) {
-	struct xpvhv_aux *iter = HvAUX(hv);
+	struct xpvhv_aux * const iter = HvAUX(hv);
 	HE * const entry = iter->xhv_eiter; /* HvEITER(hv) */
 	if (entry && HvLAZYDEL(hv)) {	/* was deleted earlier? */
 	    HvLAZYDEL_off(hv);
@@ -1875,7 +1876,7 @@ Perl_hv_iterinit(pTHX_ HV *hv)
 	iter->xhv_riter = -1; 	/* HvRITER(hv) = -1 */
 	iter->xhv_eiter = Null(HE*); /* HvEITER(hv) = Null(HE*) */
     } else {
-	S_hv_auxinit(aTHX_ hv);
+	hv_auxinit(hv);
     }
 
     /* used to be xhv->xhv_fill before 5.004_65 */
@@ -1889,7 +1890,7 @@ Perl_hv_riter_p(pTHX_ HV *hv) {
     if (!hv)
 	Perl_croak(aTHX_ "Bad hash");
 
-    iter = SvOOK(hv) ? HvAUX(hv) : S_hv_auxinit(aTHX_ hv);
+    iter = SvOOK(hv) ? HvAUX(hv) : hv_auxinit(hv);
     return &(iter->xhv_riter);
 }
 
@@ -1900,7 +1901,7 @@ Perl_hv_eiter_p(pTHX_ HV *hv) {
     if (!hv)
 	Perl_croak(aTHX_ "Bad hash");
 
-    iter = SvOOK(hv) ? HvAUX(hv) : S_hv_auxinit(aTHX_ hv);
+    iter = SvOOK(hv) ? HvAUX(hv) : hv_auxinit(hv);
     return &(iter->xhv_eiter);
 }
 
@@ -1917,7 +1918,7 @@ Perl_hv_riter_set(pTHX_ HV *hv, I32 riter) {
 	if (riter == -1)
 	    return;
 
-	iter = S_hv_auxinit(aTHX_ hv);
+	iter = hv_auxinit(hv);
     }
     iter->xhv_riter = riter;
 }
@@ -1937,7 +1938,7 @@ Perl_hv_eiter_set(pTHX_ HV *hv, HE *eiter) {
 	if (!eiter)
 	    return;
 
-	iter = S_hv_auxinit(aTHX_ hv);
+	iter = hv_auxinit(hv);
     }
     iter->xhv_eiter = eiter;
 }
@@ -1960,7 +1961,7 @@ Perl_hv_name_set(pTHX_ HV *hv, const char *name, I32 len, int flags)
 	if (name == 0)
 	    return;
 
-	iter = S_hv_auxinit(aTHX_ hv);
+	iter = hv_auxinit(hv);
     }
     PERL_HASH(hash, name, len);
     iter->xhv_name = name ? share_hek(name, len, hash) : 0;
@@ -1968,9 +1969,7 @@ Perl_hv_name_set(pTHX_ HV *hv, const char *name, I32 len, int flags)
 
 AV **
 Perl_hv_backreferences_p(pTHX_ HV *hv) {
-    struct xpvhv_aux *iter;
-
-    iter = SvOOK(hv) ? HvAUX(hv) : S_hv_auxinit(aTHX_ hv);
+    struct xpvhv_aux * const iter = SvOOK(hv) ? HvAUX(hv) : hv_auxinit(hv);
     return &(iter->xhv_backreferences);
 }
 
diff --git a/mg.c b/mg.c
index d6e76676e9..3e3ebfd3c5 100644
--- a/mg.c
+++ b/mg.c
@@ -643,7 +643,8 @@ Perl_magic_len(pTHX_ SV *sv, MAGIC *mg)
 
 #define SvRTRIM(sv) STMT_START { \
     STRLEN len = SvCUR(sv); \
-    while (len > 0 && isSPACE(SvPVX(sv)[len-1])) \
+    char * const p = SvPVX(sv); \
+    while (len > 0 && isSPACE(p[len-1])) \
 	--len; \
     SvCUR_set(sv, len); \
 } STMT_END
@@ -1257,7 +1258,7 @@ Perl_magic_clearsig(pTHX_ SV *sv, MAGIC *mg)
     		PL_psig_name[i]=0;
     	    }
     	    if(PL_psig_ptr[i]) {
-                SV *to_dec=PL_psig_ptr[i];
+		SV * const to_dec=PL_psig_ptr[i];
     		PL_psig_ptr[i]=0;
 		LEAVE;
     		SvREFCNT_dec(to_dec);
@@ -1964,12 +1965,11 @@ Perl_magic_getvec(pTHX_ SV *sv, MAGIC *mg)
     SV * const lsv = LvTARG(sv);
     PERL_UNUSED_ARG(mg);
 
-    if (!lsv) {
+    if (lsv)
+	sv_setuv(sv, do_vecget(lsv, LvTARGOFF(sv), LvTARGLEN(sv)));
+    else
 	SvOK_off(sv);
-	return 0;
-    }
 
-    sv_setuv(sv, do_vecget(lsv, LvTARGOFF(sv), LvTARGLEN(sv)));
     return 0;
 }
 
diff --git a/op.c b/op.c
index 20c08315f2..09f269a7ad 100644
--- a/op.c
+++ b/op.c
@@ -792,9 +792,10 @@ Perl_scalarvoid(pTHX_ OP *o)
                      built upon these three nroff macros being used in
                      void context. The pink camel has the details in
                      the script wrapman near page 319. */
-		    if (strnEQ(SvPVX_const(sv), "di", 2) ||
-			strnEQ(SvPVX_const(sv), "ds", 2) ||
-			strnEQ(SvPVX_const(sv), "ig", 2))
+		    const char * const maybe_macro = SvPVX_const(sv);
+		    if (strnEQ(maybe_macro, "di", 2) ||
+			strnEQ(maybe_macro, "ds", 2) ||
+			strnEQ(maybe_macro, "ig", 2))
 			    useless = 0;
 		}
 	    }
@@ -1582,13 +1583,12 @@ S_apply_attrs(pTHX_ HV *stash, SV *target, OP *attrs, bool for_my)
 	    ; 		/* already in %INC */
 	else
 	    Perl_load_module(aTHX_ PERL_LOADMOD_NOIMPORT,
-			     newSVpvn(ATTRSMODULE, sizeof(ATTRSMODULE)-1),
-			     Nullsv);
+			     newSVpvs(ATTRSMODULE), NULL);
     }
     else {
 	Perl_load_module(aTHX_ PERL_LOADMOD_IMPORT_OPS,
-			 newSVpvn(ATTRSMODULE, sizeof(ATTRSMODULE)-1),
-			 Nullsv,
+			 newSVpvs(ATTRSMODULE),
+			 NULL,
 			 prepend_elem(OP_LIST,
 				      newSVOP(OP_CONST, 0, stashsv),
 				      prepend_elem(OP_LIST,
@@ -1617,7 +1617,7 @@ S_apply_attrs_my(pTHX_ HV *stash, OP *target, OP *attrs, OP **imopsp)
     apply_attrs(stash, PAD_SV(target->op_targ), attrs, TRUE);
 
     /* Need package name for method call. */
-    pack = newSVOP(OP_CONST, 0, newSVpvn(ATTRSMODULE, sizeof(ATTRSMODULE)-1));
+    pack = newSVOP(OP_CONST, 0, newSVpvs(ATTRSMODULE));
 
     /* Build up the real arg-list. */
     stashsv = stash ? newSVhek(HvNAME_HEK(stash)) : &PL_sv_no;
@@ -1682,7 +1682,7 @@ Perl_apply_attrs_string(pTHX_ const char *stashpv, CV *cv,
     }
 
     Perl_load_module(aTHX_ PERL_LOADMOD_IMPORT_OPS,
-                     newSVpvn(ATTRSMODULE, sizeof(ATTRSMODULE)-1),
+		     newSVpvs(ATTRSMODULE),
                      Nullsv, prepend_elem(OP_LIST,
 				  newSVOP(OP_CONST, 0, newSVpv(stashpv,0)),
 				  prepend_elem(OP_LIST,
@@ -2055,8 +2055,7 @@ OP *
 Perl_jmaybe(pTHX_ OP *o)
 {
     if (o->op_type == OP_LIST) {
-	OP *o2;
-	o2 = newSVREF(newGVOP(OP_GV, 0, gv_fetchpv(";", GV_ADD, SVt_PV))),
+	OP * const o2 = newSVREF(newGVOP(OP_GV, 0, gv_fetchpv(";", GV_ADD, SVt_PV)));
 	o = convert(OP_JOIN, 0, prepend_elem(OP_LIST, o2, o));
     }
     return o;
@@ -2827,7 +2826,7 @@ Perl_pmruntime(pTHX_ OP *o, OP *expr, bool isreg)
 
     if (expr->op_type == OP_CONST) {
 	STRLEN plen;
-	SV *pat = ((SVOP*)expr)->op_sv;
+	SV * const pat = ((SVOP*)expr)->op_sv;
 	const char *p = SvPV_const(pat, plen);
 	if ((o->op_flags & OPf_SPECIAL) && (*p == ' ' && p[1] == '\0')) {
 	    U32 was_readonly = SvREADONLY(pat);
@@ -2895,7 +2894,7 @@ Perl_pmruntime(pTHX_ OP *o, OP *expr, bool isreg)
     if (repl) {
 	OP *curop;
 	if (pm->op_pmflags & PMf_EVAL) {
-	    curop = 0;
+	    curop = NULL;
 	    if (CopLINE(PL_curcop) < (line_t)PL_multi_end)
 		CopLINE_set(PL_curcop, (line_t)PL_multi_end);
 	}
@@ -2906,7 +2905,7 @@ Perl_pmruntime(pTHX_ OP *o, OP *expr, bool isreg)
 	    for (curop = LINKLIST(repl); curop!=repl; curop = LINKLIST(curop)) {
 		if (PL_opargs[curop->op_type] & OA_DANGEROUS) {
 		    if (curop->op_type == OP_GV) {
-			GV *gv = cGVOPx_gv(curop);
+			GV * const gv = cGVOPx_gv(curop);
 			repl_has_vars = 1;
 			if (strchr("&`'123456789+-\016\022", *GvENAME(gv)))
 			    break;
diff --git a/pad.c b/pad.c
index d13cd758e9..3ab7497301 100644
--- a/pad.c
+++ b/pad.c
@@ -411,6 +411,7 @@ Perl_pad_alloc(pTHX_ I32 optype, U32 tmptype)
     SV *sv;
     I32 retval;
 
+    PERL_UNUSED_ARG(optype);
     ASSERT_CURPAD_ACTIVE("pad_alloc");
 
     if (AvARRAY(PL_comppad) != PL_curpad)
diff --git a/pp_ctl.c b/pp_ctl.c
index 05b34bf414..193f0e29ab 100644
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -244,7 +244,7 @@ PP(pp_substcont)
 	    SvLEN_set(targ, SvLEN(dstr));
 	    if (DO_UTF8(dstr))
 		SvUTF8_on(targ);
-	    SvPV_set(dstr, (char*)0);
+	    SvPV_set(dstr, NULL);
 	    sv_free(dstr);
 
 	    TAINT_IF(cx->sb_rxtainted & 1);
diff --git a/pp_hot.c b/pp_hot.c
index c48333abc4..38ad000c36 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -123,10 +123,10 @@ PP(pp_sassign)
     if (PL_tainting && PL_tainted && !SvTAINTED(left))
 	TAINT_NOT;
     if (PL_op->op_private & OPpASSIGN_CV_TO_GV) {
-	SV *cv = SvRV(left);
+	SV * const cv = SvRV(left);
 	const U32 cv_type = SvTYPE(cv);
 	const U32 gv_type = SvTYPE(right);
-	bool got_coderef = cv_type == SVt_PVCV || cv_type == SVt_PVFM;
+	const bool got_coderef = cv_type == SVt_PVCV || cv_type == SVt_PVFM;
 
 	if (!got_coderef) {
 	    assert(SvROK(cv));
@@ -137,7 +137,7 @@ PP(pp_sassign)
 	   context. */
 	if (!got_coderef && gv_type != SVt_PVGV && GIMME_V == G_VOID) {
 	    /* Is the target symbol table currently empty?  */
-	    GV *gv = gv_fetchsv(right, GV_NOINIT, SVt_PVGV);
+	    GV * const gv = gv_fetchsv(right, GV_NOINIT, SVt_PVGV);
 	    if (SvTYPE(gv) != SVt_PVGV && !SvOK(gv)) {
 		/* Good. Create a new proxy constant subroutine in the target.
 		   The gv becomes a(nother) reference to the constant.  */
@@ -401,11 +401,12 @@ PP(pp_or)
 PP(pp_defined)
 {
     dVAR; dSP;
-    register SV* sv = NULL;
-    bool defined = FALSE;
+    register SV* sv;
+    bool defined;
     const int op_type = PL_op->op_type;
+    const int is_dor = (op_type == OP_DOR || op_type == OP_DORASSIGN);
 
-    if(op_type == OP_DOR || op_type == OP_DORASSIGN) {
+    if (is_dor) {
         sv = TOPs;
         if (!sv || !SvANY(sv)) {
 	    if (op_type == OP_DOR)
@@ -419,6 +420,7 @@ PP(pp_defined)
     } else
         DIE(aTHX_ "panic:  Invalid op (%s) in pp_defined()", OP_NAME(PL_op));
 
+    defined = FALSE;
     switch (SvTYPE(sv)) {
     case SVt_PVAV:
 	if (AvMAX(sv) >= 0 || SvGMAGICAL(sv) || (SvRMAGICAL(sv) && mg_find(sv, PERL_MAGIC_tied)))
@@ -436,9 +438,10 @@ PP(pp_defined)
 	SvGETMAGIC(sv);
 	if (SvOK(sv))
 	    defined = TRUE;
+	break;
     }
-    
-    if(op_type == OP_DOR || op_type == OP_DORASSIGN) {
+
+    if (is_dor) {
         if(defined) 
             RETURN; 
         if(op_type == OP_DOR)
@@ -1105,10 +1108,8 @@ PP(pp_aassign)
 
 		while (relem < lastrelem) {	/* gobble up all the rest */
 		    HE *didstore;
-		    if (*relem)
-			sv = *(relem++);
-		    else
-			sv = &PL_sv_no, relem++;
+		    sv = *relem ? *relem : &PL_sv_no;
+		    relem++;
 		    tmpstr = NEWSV(29,0);
 		    if (*relem)
 			sv_setsv(tmpstr,*relem);	/* value */
@@ -1400,11 +1401,11 @@ play_it_again:
 	}
 	if (global) {
 	    if (dynpm->op_pmflags & PMf_CONTINUE) {
-		MAGIC* mg = 0;
+		MAGIC* mg = NULL;
 		if (SvTYPE(TARG) >= SVt_PVMG && SvMAGIC(TARG))
 		    mg = mg_find(TARG, PERL_MAGIC_regex_global);
 		if (!mg) {
-		    sv_magic(TARG, (SV*)0, PERL_MAGIC_regex_global, Nullch, 0);
+		    sv_magic(TARG, NULL, PERL_MAGIC_regex_global, NULL, 0);
 		    mg = mg_find(TARG, PERL_MAGIC_regex_global);
 		}
 		if (rx->startp[0] != -1) {
@@ -1434,7 +1435,7 @@ play_it_again:
 	    else
 		mg = NULL;
 	    if (!mg) {
-		sv_magic(TARG, (SV*)0, PERL_MAGIC_regex_global, Nullch, 0);
+		sv_magic(TARG, NULL, PERL_MAGIC_regex_global, NULL, 0);
 		mg = mg_find(TARG, PERL_MAGIC_regex_global);
 	    }
 	    if (rx->startp[0] != -1) {
@@ -1459,7 +1460,7 @@ yup:					/* Confirmed by INTUIT */
     if (RX_MATCH_COPIED(rx))
 	Safefree(rx->subbeg);
     RX_MATCH_COPIED_off(rx);
-    rx->subbeg = Nullch;
+    rx->subbeg = NULL;
     if (global) {
 	/* FIXME - should rx->subbeg be const char *?  */
 	rx->subbeg = (char *) truebase;
@@ -1513,7 +1514,7 @@ nope:
 ret_no:
     if (global && !(dynpm->op_pmflags & PMf_CONTINUE)) {
 	if (SvTYPE(TARG) >= SVt_PVMG && SvMAGIC(TARG)) {
-	    MAGIC* mg = mg_find(TARG, PERL_MAGIC_regex_global);
+	    MAGIC* const mg = mg_find(TARG, PERL_MAGIC_regex_global);
 	    if (mg)
 		mg->mg_len = -1;
 	}
@@ -1535,22 +1536,24 @@ Perl_do_readline(pTHX)
     register IO * const io = GvIO(PL_last_in_gv);
     register const I32 type = PL_op->op_type;
     const I32 gimme = GIMME_V;
-    MAGIC *mg;
 
-    if (io && (mg = SvTIED_mg((SV*)io, PERL_MAGIC_tiedscalar))) {
-	PUSHMARK(SP);
-	XPUSHs(SvTIED_obj((SV*)io, mg));
-	PUTBACK;
-	ENTER;
-	call_method("READLINE", gimme);
-	LEAVE;
-	SPAGAIN;
-	if (gimme == G_SCALAR) {
-	    SV* result = POPs;
-	    SvSetSV_nosteal(TARG, result);
-	    PUSHTARG;
+    if (io) {
+	MAGIC * const mg = SvTIED_mg((SV*)io, PERL_MAGIC_tiedscalar);
+	if (mg) {
+	    PUSHMARK(SP);
+	    XPUSHs(SvTIED_obj((SV*)io, mg));
+	    PUTBACK;
+	    ENTER;
+	    call_method("READLINE", gimme);
+	    LEAVE;
+	    SPAGAIN;
+	    if (gimme == G_SCALAR) {
+		SV* const result = POPs;
+		SvSetSV_nosteal(TARG, result);
+		PUSHTARG;
+	    }
+	    RETURN;
 	}
-	RETURN;
     }
     fp = Nullfp;
     if (io) {
@@ -1677,11 +1680,10 @@ Perl_do_readline(pTHX)
 	SPAGAIN;
 	XPUSHs(sv);
 	if (type == OP_GLOB) {
-	    char *tmps;
 	    const char *t1;
 
 	    if (SvCUR(sv) > 0 && SvCUR(PL_rs) > 0) {
-		tmps = SvEND(sv) - 1;
+		char * const tmps = SvEND(sv) - 1;
 		if (*tmps == *SvPVX_const(PL_rs)) {
 		    *tmps = '\0';
 		    SvCUR_set(sv, SvCUR(sv) - 1);
@@ -1779,7 +1781,7 @@ PP(pp_helem)
 
 	}
 	he = hv_fetch_ent(hv, keysv, lval && !defer, hash);
-	svp = he ? &HeVAL(he) : 0;
+	svp = he ? &HeVAL(he) : NULL;
     }
     else {
 	RETPUSHUNDEF;
@@ -1794,7 +1796,7 @@ PP(pp_helem)
 	    lv = sv_newmortal();
 	    sv_upgrade(lv, SVt_PVLV);
 	    LvTYPE(lv) = 'y';
-	    sv_magic(lv, key2 = newSVsv(keysv), PERL_MAGIC_defelem, Nullch, 0);
+	    sv_magic(lv, key2 = newSVsv(keysv), PERL_MAGIC_defelem, NULL, 0);
 	    SvREFCNT_dec(key2);	/* sv_magic() increments refcount */
 	    LvTARG(lv) = SvREFCNT_inc(hv);
 	    LvTARGLEN(lv) = 1;
@@ -2000,7 +2002,7 @@ PP(pp_iter)
 	    lv = cx->blk_loop.iterlval = NEWSV(26, 0);
 	    sv_upgrade(lv, SVt_PVLV);
 	    LvTYPE(lv) = 'y';
-	    sv_magic(lv, Nullsv, PERL_MAGIC_defelem, Nullch, 0);
+	    sv_magic(lv, NULL, PERL_MAGIC_defelem, NULL, 0);
 	}
 	LvTARG(lv) = SvREFCNT_inc(av);
 	LvTARGOFF(lv) = cx->blk_loop.iterix;
@@ -2143,7 +2145,7 @@ PP(pp_subst)
 	}
     }
     else {
-        c = Nullch;
+	c = NULL;
 	doutf8 = FALSE;
     }
     
@@ -2329,7 +2331,7 @@ PP(pp_subst)
 	SvCUR_set(TARG, SvCUR(dstr));
 	SvLEN_set(TARG, SvLEN(dstr));
 	doutf8 |= DO_UTF8(dstr);
-	SvPV_set(dstr, (char*)0);
+	SvPV_set(dstr, NULL);
 	sv_free(dstr);
 
 	TAINT_IF(rxtainted & 1);
@@ -2654,7 +2656,7 @@ S_get_db_sub(pTHX_ SV **svp, CV *cv)
 	    SvREFCNT_dec(tmp);
 	}
 	else {
-	    gv_efullname3(dbsv, gv, Nullch);
+	    gv_efullname3(dbsv, gv, NULL);
 	}
     }
     else {
@@ -2707,7 +2709,7 @@ PP(pp_entersub)
 		mg_get(sv);
 		if (SvROK(sv))
 		    goto got_rv;
-		sym = SvPOKp(sv) ? SvPVX_const(sv) : Nullch;
+		sym = SvPOKp(sv) ? SvPVX_const(sv) : NULL;
 	    }
 	    else {
 		sym = SvPV_nolen_const(sv);
@@ -2764,7 +2766,7 @@ try_autoload:
 	    /* sorry */
 	    else {
 		sub_name = sv_newmortal();
-		gv_efullname3(sub_name, gv, Nullch);
+		gv_efullname3(sub_name, gv, NULL);
 		DIE(aTHX_ "Undefined subroutine &%"SVf" called", sub_name);
 	    }
 	}
@@ -2924,7 +2926,7 @@ Perl_sub_crush_depth(pTHX_ CV *cv)
 	Perl_warner(aTHX_ packWARN(WARN_RECURSION), "Deep recursion on anonymous subroutine");
     else {
 	SV* const tmpstr = sv_newmortal();
-	gv_efullname3(tmpstr, CvGV(cv), Nullch);
+	gv_efullname3(tmpstr, CvGV(cv), NULL);
 	Perl_warner(aTHX_ packWARN(WARN_RECURSION), "Deep recursion on subroutine \"%"SVf"\"",
 		tmpstr);
     }
@@ -2969,7 +2971,7 @@ PP(pp_aelem)
 	    lv = sv_newmortal();
 	    sv_upgrade(lv, SVt_PVLV);
 	    LvTYPE(lv) = 'y';
-	    sv_magic(lv, Nullsv, PERL_MAGIC_defelem, Nullch, 0);
+	    sv_magic(lv, Nullsv, PERL_MAGIC_defelem, NULL, 0);
 	    LvTARG(lv) = SvREFCNT_inc(av);
 	    LvTARGOFF(lv) = elem;
 	    LvTARGLEN(lv) = 1;
@@ -3053,7 +3055,7 @@ S_method_common(pTHX_ SV* meth, U32* hashp)
     GV* gv;
     HV* stash;
     STRLEN namelen;
-    const char* packname = Nullch;
+    const char* packname = NULL;
     SV *packsv = Nullsv;
     STRLEN packlen;
     const char * const name = SvPV_const(meth, namelen);
@@ -3144,7 +3146,7 @@ S_method_common(pTHX_ SV* meth, U32* hashp)
 	   don't want that.
 	*/
 	const char* leaf = name;
-	const char* sep = Nullch;
+	const char* sep = NULL;
 	const char* p;
 
 	for (p = name; *p; p++) {
diff --git a/pp_sys.c b/pp_sys.c
index e1c6125dc9..fa5c59e7c6 100644
--- a/pp_sys.c
+++ b/pp_sys.c
@@ -1932,8 +1932,6 @@ PP(pp_eof)
 {
     dVAR; dSP;
     GV *gv;
-    IO *io;
-    MAGIC *mg;
 
     if (MAXARG == 0) {
 	if (PL_op->op_flags & OPf_SPECIAL) {	/* eof() */
@@ -1958,17 +1956,19 @@ PP(pp_eof)
     else
 	gv = PL_last_in_gv = (GV*)POPs;		/* eof(FH) */
 
-    if (gv && (io = GvIO(gv))
-	&& (mg = SvTIED_mg((SV*)io, PERL_MAGIC_tiedscalar)))
-    {
-	PUSHMARK(SP);
-	XPUSHs(SvTIED_obj((SV*)io, mg));
-	PUTBACK;
-	ENTER;
-	call_method("EOF", G_SCALAR);
-	LEAVE;
-	SPAGAIN;
-	RETURN;
+    if (gv) {
+	IO * const io = GvIO(gv);
+	MAGIC * mg;
+	if (io && (mg = SvTIED_mg((SV*)io, PERL_MAGIC_tiedscalar))) {
+	    PUSHMARK(SP);
+	    XPUSHs(SvTIED_obj((SV*)io, mg));
+	    PUTBACK;
+	    ENTER;
+	    call_method("EOF", G_SCALAR);
+	    LEAVE;
+	    SPAGAIN;
+	    RETURN;
+	}
     }
 
     PUSHs(boolSV(!gv || do_eof(gv)));
@@ -3543,7 +3543,7 @@ S_dooneliner(pTHX_ const char *cmd, const char *filename)
 		 ; e++)
 	    {
 		/* you don't see this */
-		char *errmsg =
+		const char * const errmsg =
 #ifdef HAS_SYS_ERRLIST
 		    sys_errlist[e]
 #else
@@ -5194,18 +5194,16 @@ PP(pp_ggrent)
 {
 #ifdef HAS_GROUP
     dVAR; dSP;
-    I32 which = PL_op->op_type;
-    register char **elem;
-    register SV *sv;
-    struct group *grent;
+    const I32 which = PL_op->op_type;
+    const struct group *grent;
 
     if (which == OP_GGRNAM) {
 	const char* const name = POPpbytex;
-	grent = (struct group *)getgrnam(name);
+	grent = (const struct group *)getgrnam(name);
     }
     else if (which == OP_GGRGID) {
 	const Gid_t gid = POPi;
-	grent = (struct group *)getgrgid(gid);
+	grent = (const struct group *)getgrgid(gid);
     }
     else
 #ifdef HAS_GETGRENT
@@ -5216,7 +5214,9 @@ PP(pp_ggrent)
 
     EXTEND(SP, 4);
     if (GIMME != G_ARRAY) {
-	PUSHs(sv = sv_newmortal());
+	SV * const sv = sv_newmortal();
+
+	PUSHs(sv);
 	if (grent) {
 	    if (which == OP_GGRNAM)
 		sv_setiv(sv, (IV)grent->gr_gid);
@@ -5227,6 +5227,8 @@ PP(pp_ggrent)
     }
 
     if (grent) {
+	SV *sv;
+	char **elem;
 	PUSHs(sv = sv_mortalcopy(&PL_sv_no));
 	sv_setpv(sv, grent->gr_name);
 
diff --git a/proto.h b/proto.h
index 3bd2ced1d7..d94b93a131 100644
--- a/proto.h
+++ b/proto.h
@@ -3594,7 +3594,6 @@ STATIC bool	S_reginclass(pTHX_ const regnode *n, const U8 *p, STRLEN *lenp, bool
 
 STATIC CHECKPOINT	S_regcppush(pTHX_ I32 parenfloor);
 STATIC char*	S_regcppop(pTHX);
-STATIC char*	S_regcp_set_to(pTHX_ I32 ss);
 STATIC void	S_cache_re(pTHX_ regexp *prog)
 			__attribute__nonnull__(pTHX_1);
 
diff --git a/reentr.c b/reentr.c
index 0657791462..4dcaf8052b 100644
--- a/reentr.c
+++ b/reentr.c
@@ -2,7 +2,7 @@
  *
  *    reentr.c
  *
- *    Copyright (C) 2002, 2003, 2005 by Larry Wall and others
+ *    Copyright (C) 2002, 2003, 2005, 2006 by Larry Wall and others
  *
  *    You may distribute under the terms of either the GNU General Public
  *    License or the Artistic License, as specified in the README file.
diff --git a/reentr.h b/reentr.h
index 9ee49a427b..ca526c456b 100644
--- a/reentr.h
+++ b/reentr.h
@@ -2,7 +2,7 @@
  *
  *    reentr.h
  *
- *    Copyright (C) 2002, 2003, 2005 by Larry Wall and others
+ *    Copyright (C) 2002, 2003, 2005, 2006 by Larry Wall and others
  *
  *    You may distribute under the terms of either the GNU General Public
  *    License or the Artistic License, as specified in the README file.
diff --git a/regcomp.c b/regcomp.c
index 86b9140b9f..12bfc1c491 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -282,27 +282,6 @@ static const scan_data_t zero_scan_data =
 } STMT_END
 
 /*
- * Calls SAVEDESTRUCTOR_X if needed, then calls Perl_croak with the given
- * args. Show regex, up to a maximum length. If it's too long, chop and add
- * "...".
- */
-#define	FAIL2(pat,msg) STMT_START {					\
-    const char *ellipses = "";						\
-    IV len = RExC_end - RExC_precomp;					\
-									\
-    if (!SIZE_ONLY)							\
-	SAVEDESTRUCTOR_X(clear_re,(void*)RExC_rx);			\
-    if (len > RegexLengthToShowInErrorMessages) {			\
-	/* chop 10 shorter than the max, to ensure meaning of "..." */	\
-	len = RegexLengthToShowInErrorMessages - 10;			\
-	ellipses = "...";						\
-    }									\
-    S_re_croak2(aTHX_ pat, " in regex m/%.*s%s/",			\
-	    msg, (int)len, RExC_precomp, ellipses);			\
-} STMT_END
-
-
-/*
  * Simple_vFAIL -- like FAIL, but marks the current location in the scan
  */
 #define	Simple_vFAIL(m) STMT_START {					\
@@ -765,7 +744,7 @@ and would end up looking like:
     DEBUG_TRIE_COMPILE_r({                                                 \
 	SV *tmp;                                                           \
 	if ( UTF ) {                                                       \
-	    tmp = newSVpvn( "", 0 );                                       \
+	    tmp = newSVpvs( "" );                                          \
 	    pv_uni_display( tmp, uc, len, 60, UNI_DISPLAY_REGEX );         \
 	} else {                                                           \
 	    tmp = Perl_newSVpvf_nocontext( "%c", (int)uvc );               \
@@ -2051,7 +2030,7 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp, I32 *deltap,
 	    if (flags & SCF_DO_SUBSTR)
 		scan_commit(pRExC_state, data);
 	    if (UTF) {
-		U8 *s = (U8 *)STRING(scan);
+		const U8 * const s = (U8 *)STRING(scan);
 		l = utf8_length(s, s + l);
 		uc = utf8_to_uvchr(s, NULL);
 	    }
@@ -3222,21 +3201,20 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp)
     register I32 parno = 0;
     I32 flags;
     const I32 oregflags = RExC_flags;
-    I32 have_branch = 0;
-    I32 open = 0;
+    bool have_branch = 0;
+    bool is_open = 0;
 
     /* for (?g), (?gc), and (?o) warnings; warning
        about (?c) will warn about (?g) -- japhy    */
 
+#define WASTED_O  0x01
+#define WASTED_G  0x02
+#define WASTED_C  0x04
+#define WASTED_GC (0x02|0x04)
     I32 wastedflags = 0x00;
-    const I32 wasted_o  = 0x01;
-    const I32 wasted_g  = 0x02;
-    const I32 wasted_gc = 0x02 | 0x04;
-    const I32 wasted_c  = 0x04;
 
     char * parse_start = RExC_parse; /* MJD */
     char * const oregcomp_parse = RExC_parse;
-    char c;
 
     *flagp = 0;				/* Tentatively. */
 
@@ -3246,7 +3224,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp)
 	if (*RExC_parse == '?') { /* (?...) */
 	    U32 posflags = 0, negflags = 0;
 	    U32 *flagsp = &posflags;
-	    int logical = 0;
+	    bool is_logical = 0;
 	    const char * const seqstart = RExC_parse;
 
 	    RExC_parse++;
@@ -3283,7 +3261,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp)
 		    vWARNdep(RExC_parse, "(?p{}) is deprecated - use (??{})");
 		/* FALL THROUGH*/
 	    case '?':           /* (??...) */
-		logical = 1;
+		is_logical = 1;
 		if (*RExC_parse != '{')
 		    goto unknown;
 		paren = *RExC_parse++;
@@ -3293,32 +3271,28 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp)
 		I32 count = 1, n = 0;
 		char c;
 		char *s = RExC_parse;
-		SV *sv;
-		OP_4tree *sop, *rop;
 
 		RExC_seen_zerolen++;
 		RExC_seen |= REG_SEEN_EVAL;
 		while (count && (c = *RExC_parse)) {
-		    if (c == '\\' && RExC_parse[1])
-			RExC_parse++;
+		    if (c == '\\') {
+			if (RExC_parse[1])
+			    RExC_parse++;
+		    }
 		    else if (c == '{')
 			count++;
 		    else if (c == '}')
 			count--;
 		    RExC_parse++;
 		}
-		if (*RExC_parse != ')')
-		{
+		if (*RExC_parse != ')') {
 		    RExC_parse = s;		
 		    vFAIL("Sequence (?{...}) not terminated or not {}-balanced");
 		}
 		if (!SIZE_ONLY) {
 		    PAD *pad;
-		
-		    if (RExC_parse - 1 - s)
-			sv = newSVpvn(s, RExC_parse - 1 - s);
-		    else
-			sv = newSVpvs("");
+		    OP_4tree *sop, *rop;
+		    SV * const sv = newSVpvn(s, RExC_parse - 1 - s);
 
 		    ENTER;
 		    Perl_save_re_context(aTHX);
@@ -3347,7 +3321,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp)
 		}
 
 		nextchar(pRExC_state);
-		if (logical) {
+		if (is_logical) {
 		    ret = reg_node(pRExC_state, LOGICAL);
 		    if (!SIZE_ONLY)
 			ret->flags = 2;
@@ -3377,6 +3351,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp)
 		}
 		else if (RExC_parse[0] >= '1' && RExC_parse[0] <= '9' ) {
                     /* (?(1)...) */
+		    char c;
 		    parno = atoi(RExC_parse++);
 
 		    while (isDIGIT(*RExC_parse))
@@ -3434,7 +3409,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp)
 
 		    if (*RExC_parse == 'o' || *RExC_parse == 'g') {
 			if (SIZE_ONLY && ckWARN(WARN_REGEXP)) {
-			    I32 wflagbit = *RExC_parse == 'o' ? wasted_o : wasted_g;
+			    const I32 wflagbit = *RExC_parse == 'o' ? WASTED_O : WASTED_G;
 			    if (! (wastedflags & wflagbit) ) {
 				wastedflags |= wflagbit;
 				vWARN5(
@@ -3450,8 +3425,8 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp)
 		    }
 		    else if (*RExC_parse == 'c') {
 			if (SIZE_ONLY && ckWARN(WARN_REGEXP)) {
-			    if (! (wastedflags & wasted_c) ) {
-				wastedflags |= wasted_gc;
+			    if (! (wastedflags & WASTED_C) ) {
+				wastedflags |= WASTED_GC;
 				vWARN3(
 				    RExC_parse + 1,
 				    "Useless (%sc) - %suse /gc modifier",
@@ -3494,7 +3469,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp)
 	    ret = reganode(pRExC_state, OPEN, parno);
             Set_Node_Length(ret, 1); /* MJD */
             Set_Node_Offset(ret, RExC_parse); /* MJD */
-	    open = 1;
+	    is_open = 1;
 	}
     }
     else                        /* ! paren */
@@ -3523,7 +3498,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp)
     else if (paren == ':') {
 	*flagp |= flags&SIMPLE;
     }
-    if (open) {				/* Starts with OPEN. */
+    if (is_open) {				/* Starts with OPEN. */
 	regtail(pRExC_state, ret, br);		/* OPEN -> first. */
     }
     else if (paren != '?')		/* Not Conditional */
diff --git a/regexec.c b/regexec.c
index a65ded7b3c..7ca466737c 100644
--- a/regexec.c
+++ b/regexec.c
@@ -285,18 +285,6 @@ S_regcppop(pTHX)
     return input;
 }
 
-STATIC char *
-S_regcp_set_to(pTHX_ I32 ss)
-{
-    dVAR;
-    const I32 tmp = PL_savestack_ix;
-
-    PL_savestack_ix = ss;
-    regcppop();
-    PL_savestack_ix = tmp;
-    return Nullch;
-}
-
 typedef struct re_cc_state
 {
     I32 ss;
@@ -1193,8 +1181,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
 		if (s == PL_bostr)
 		    tmp = '\n';
 		else {
-		    U8 *r = reghop3((U8*)s, -1, (U8*)PL_bostr);
-		
+		    U8 * const r = reghop3((U8*)s, -1, (U8*)PL_bostr);
 		    tmp = utf8n_to_uvchr(r, UTF8SKIP(r), 0, 0);
 		}
 		tmp = ((OP(c) == BOUND ?
@@ -1236,8 +1223,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
 		if (s == PL_bostr)
 		    tmp = '\n';
 		else {
-		    U8 *r = reghop3((U8*)s, -1, (U8*)PL_bostr);
-		
+		    U8 * const r = reghop3((U8*)s, -1, (U8*)PL_bostr);
 		    tmp = utf8n_to_uvchr(r, UTF8SKIP(r), 0, 0);
 		}
 		tmp = ((OP(c) == NBOUND ?
@@ -1651,8 +1637,8 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
     const bool do_utf8 = DO_UTF8(sv);
     const I32 multiline = prog->reganch & PMf_MULTILINE;
 #ifdef DEBUGGING
-    SV *dsv0 = PERL_DEBUG_PAD_ZERO(0);
-    SV *dsv1 = PERL_DEBUG_PAD_ZERO(1);
+    SV * const dsv0 = PERL_DEBUG_PAD_ZERO(0);
+    SV * const dsv1 = PERL_DEBUG_PAD_ZERO(1);
 #endif
 
     GET_RE_DEBUG_FLAGS_DECL;
@@ -2417,9 +2403,9 @@ S_regmatch(pTHX_ regnode *prog)
 #endif
     register const bool do_utf8 = PL_reg_match_utf8;
 #ifdef DEBUGGING
-    SV *dsv0 = PERL_DEBUG_PAD_ZERO(0);
-    SV *dsv1 = PERL_DEBUG_PAD_ZERO(1);
-    SV *dsv2 = PERL_DEBUG_PAD_ZERO(2);
+    SV * const dsv0 = PERL_DEBUG_PAD_ZERO(0);
+    SV * const dsv1 = PERL_DEBUG_PAD_ZERO(1);
+    SV * const dsv2 = PERL_DEBUG_PAD_ZERO(2);
 
     SV *re_debug_flags = NULL;
 #endif
@@ -2438,7 +2424,7 @@ S_regmatch(pTHX_ regnode *prog)
     while (scan != NULL) {
 
         DEBUG_EXECUTE_r( {
-	    SV *prop = sv_newmortal();
+	    SV * const prop = sv_newmortal();
 	    const int docolor = *PL_colors[0];
 	    const int taill = (docolor ? 10 : 7); /* 3 chars for "> <" */
 	    int l = (PL_regeol - locinput) > taill ? taill : (PL_regeol - locinput);
@@ -2762,7 +2748,7 @@ S_regmatch(pTHX_ regnode *prog)
 				    best = cur;
 			}
 			DEBUG_EXECUTE_r({
-		            SV **tmp = av_fetch( trie->words, accept_buff[ best ].wordnum - 1, 0 );
+			    SV ** const tmp = av_fetch( trie->words, accept_buff[ best ].wordnum - 1, 0 );
     			    PerlIO_printf( Perl_debug_log, "%*s  %strying alternation #%d <%s> at 0x%p%s\n",
     			        REPORT_CODE_OFF+PL_regindent*2, "", PL_colors[4],
     			        accept_buff[best].wordnum,
@@ -3204,11 +3190,11 @@ S_regmatch(pTHX_ regnode *prog)
 	case EVAL:
 	{
 	    dSP;
-	    OP_4tree *oop = PL_op;
-	    COP *ocurcop = PL_curcop;
+	    OP_4tree * const oop = PL_op;
+	    COP * const ocurcop = PL_curcop;
 	    PAD *old_comppad;
 	    SV *ret;
-	    struct regexp *oreg = PL_reg_re;
+	    struct regexp * const oreg = PL_reg_re;
 	
 	    n = ARG(scan);
 	    PL_op = (OP_4tree*)PL_regdata->data[n];
@@ -3217,7 +3203,7 @@ S_regmatch(pTHX_ regnode *prog)
 	    PL_regendp[0] = PL_reg_magic->mg_len = locinput - PL_bostr;
 
 	    {
-		SV **before = SP;
+		SV ** const before = SP;
 		CALLRUNOPS(aTHX);			/* Scalar context. */
 		SPAGAIN;
 		if (SP == before)
@@ -3234,7 +3220,7 @@ S_regmatch(pTHX_ regnode *prog)
 	    if (logical) {
 		if (logical == 2) {	/* Postponed subexpression. */
 		    regexp *re;
-		    MAGIC *mg = Null(MAGIC*);
+		    MAGIC *mg = NULL;
 		    re_cc_state state;
 		    CHECKPOINT cp, lastcp;
                     int toggleutf;
@@ -3255,7 +3241,7 @@ S_regmatch(pTHX_ regnode *prog)
 		    }
 		    else {
 			STRLEN len;
-			const char *t = SvPV_const(ret, len);
+			const char * const t = SvPV_const(ret, len);
 			PMOP pm;
 			char * const oprecomp = PL_regprecomp;
 			const I32 osize = PL_regsize;
@@ -3494,7 +3480,7 @@ S_regmatch(pTHX_ regnode *prog)
 
 		CHECKPOINT cp, lastcp;
 		CURCUR* cc = PL_regcc;
-		char *lastloc = cc->lastloc; /* Detection of 0-len. */
+		char * const lastloc = cc->lastloc; /* Detection of 0-len. */
 		I32 cache_offset = 0, cache_bit = 0;
 		
 		n = cc->cur + 1;	/* how many we know we matched */
@@ -3698,12 +3684,10 @@ S_regmatch(pTHX_ regnode *prog)
 		    next = inner;	/* Avoid recursion. */
 		else {
 		    const I32 lastparen = *PL_reglastparen;
-		    I32 unwind1;
-		    re_unwind_branch_t *uw;
-
 		    /* Put unwinding data on stack */
-		    unwind1 = SSNEWt(1,re_unwind_branch_t);
-		    uw = SSPTRt(unwind1,re_unwind_branch_t);
+		    const I32 unwind1 = SSNEWt(1,re_unwind_branch_t);
+		    re_unwind_branch_t * const uw = SSPTRt(unwind1,re_unwind_branch_t);
+
 		    uw->prev = unwind;
 		    unwind = unwind1;
 		    uw->type = ((c1 == BRANCH)
@@ -4152,14 +4136,22 @@ S_regmatch(pTHX_ regnode *prog)
 		re_cc_state *cur_call_cc = PL_reg_call_cc;
 		CURCUR *cctmp = PL_regcc;
 		regexp *re = PL_reg_re;
-		CHECKPOINT cp, lastcp;
-		
-		cp = regcppush(0);	/* Save *all* the positions. */
+		CHECKPOINT lastcp;
+		I32 tmp;
+
+		/* Save *all* the positions. */
+		const CHECKPOINT cp = regcppush(0);
 		REGCP_SET(lastcp);
-		regcp_set_to(PL_reg_call_cc->ss); /* Restore parens of
-						    the caller. */
-		PL_reginput = locinput;	/* Make position available to
-					   the callcc. */
+
+		/* Restore parens of the caller. */
+		tmp = PL_savestack_ix;
+		PL_savestack_ix = PL_reg_call_cc->ss;
+		regcppop();
+		PL_savestack_ix = tmp;
+
+		/* Make position available to the callcc. */
+		PL_reginput = locinput;
+
 		cache_re(PL_reg_call_cc->re);
 		PL_regcc = PL_reg_call_cc->cc;
 		PL_reg_call_cc = PL_reg_call_cc->prev;
@@ -4298,13 +4290,13 @@ no:
 no_final:
 do_no:
     if (unwind) {
-	re_unwind_t *uw = SSPTRt(unwind,re_unwind_t);
+	re_unwind_t * const uw = SSPTRt(unwind,re_unwind_t);
 
 	switch (uw->type) {
 	case RE_UNWIND_BRANCH:
 	case RE_UNWIND_BRANCHJ:
 	{
-	    re_unwind_branch_t *uwb = &(uw->branch);
+	    re_unwind_branch_t * const uwb = &(uw->branch);
 	    const I32 lastparen = uwb->lastparen;
 	
 	    REGCP_UNWIND(uwb->lastcp);
@@ -4586,7 +4578,7 @@ S_regrepeat(pTHX_ const regnode *p, I32 max)
 
     DEBUG_r({
 	        SV *re_debug_flags = NULL;
-		SV *prop = sv_newmortal();
+		SV * const prop = sv_newmortal();
                 GET_RE_DEBUG_FLAGS;
                 DEBUG_EXECUTE_r({
 		regprop(prop, p);
diff --git a/sv.c b/sv.c
index b2cd1d8e9b..72412f7999 100644
--- a/sv.c
+++ b/sv.c
@@ -1090,14 +1090,14 @@ Perl_sv_upgrade(pTHX_ register SV *sv, U32 new_type)
 
 	/* Could put this in the else clause below, as PVMG must have SvPVX
 	   0 already (the assertion above)  */
-	SvPV_set(sv, (char*)0);
+	SvPV_set(sv, NULL);
 
 	if (old_type >= SVt_PVMG) {
 	    SvMAGIC_set(sv, ((XPVMG*)old_body)->xmg_magic);
 	    SvSTASH_set(sv, ((XPVMG*)old_body)->xmg_stash);
 	} else {
-	    SvMAGIC_set(sv, 0);
-	    SvSTASH_set(sv, 0);
+	    SvMAGIC_set(sv, NULL);
+	    SvSTASH_set(sv, NULL);
 	}
 	break;
 
@@ -1149,7 +1149,7 @@ Perl_sv_upgrade(pTHX_ register SV *sv, U32 new_type)
 	if (new_type == SVt_PVIO)
 	    IoPAGE_LEN(sv) = 60;
 	if (old_type < SVt_RV)
-	    SvPV_set(sv, 0);
+	    SvPV_set(sv, NULL);
 	break;
     default:
 	Perl_croak(aTHX_ "panic: sv_upgrade to unknown type %lu",
@@ -3394,7 +3394,7 @@ Perl_sv_setsv_flags(pTHX_ SV *dstr, register SV *sstr, I32 flags)
 
                 SvTEMP_off(dstr);
                 (void)SvOK_off(sstr);	/* NOTE: nukes most SvFLAGS on sstr */
-                SvPV_set(sstr, Nullch);
+                SvPV_set(sstr, NULL);
                 SvLEN_set(sstr, 0);
                 SvCUR_set(sstr, 0);
                 SvTEMP_off(sstr);
@@ -3781,7 +3781,7 @@ Perl_sv_force_normal_flags(pTHX_ register SV *sv, U32 flags)
             SvFAKE_off(sv);
             SvREADONLY_off(sv);
             /* This SV doesn't own the buffer, so need to Newx() a new one:  */
-            SvPV_set(sv, (char*)0);
+            SvPV_set(sv, NULL);
             SvLEN_set(sv, 0);
             if (flags & SV_COW_DROP_PV) {
                 /* OK, so we don't need to copy our buffer.  */
@@ -8939,8 +8939,8 @@ ptr_table_* functions.
 #define io_dup_inc(s,t)	(IO*)SvREFCNT_inc(sv_dup((SV*)s,t))
 #define gv_dup(s,t)	(GV*)sv_dup((SV*)s,t)
 #define gv_dup_inc(s,t)	(GV*)SvREFCNT_inc(sv_dup((SV*)s,t))
-#define SAVEPV(p)	(p ? savepv(p) : Nullch)
-#define SAVEPVN(p,n)	(p ? savepvn(p,n) : Nullch)
+#define SAVEPV(p)	((p) ? savepv(p) : NULL)
+#define SAVEPVN(p,n)	((p) ? savepvn(p,n) : NULL)
 
 
 /* Duplicate a regexp. Required reading: pregcomp() and pregfree() in
@@ -9372,7 +9372,7 @@ Perl_rvpv_dup(pTHX_ SV *dstr, const SV *sstr, CLONE_PARAMS* param)
 	if (SvTYPE(dstr) == SVt_RV)
 	    SvRV_set(dstr, NULL);
 	else
-	    SvPV_set(dstr, 0);
+	    SvPV_set(dstr, NULL);
     }
 }
 
@@ -9385,7 +9385,7 @@ Perl_sv_dup(pTHX_ const SV *sstr, CLONE_PARAMS* param)
     SV *dstr;
 
     if (!sstr || SvTYPE(sstr) == SVTYPEMASK)
-	return Nullsv;
+	return NULL;
     /* look for it in the table first */
     dstr = (SV*)ptr_table_fetch(PL_ptr_table, sstr);
     if (dstr)
@@ -10851,7 +10851,7 @@ perl_clone_using(PerlInterpreter *proto_perl, UV flags,
 	 * orphaned
 	 */
 	for (i = 0; i<= proto_perl->Ttmps_ix; i++) {
-	    SV *nsv = (SV*)ptr_table_fetch(PL_ptr_table,
+	    SV * const nsv = (SV*)ptr_table_fetch(PL_ptr_table,
 		    proto_perl->Ttmps_stack[i]);
 	    if (nsv && !SvREFCNT(nsv)) {
 		EXTEND_MORTAL(1);
diff --git a/toke.c b/toke.c
index 139a1212cc..d539b07771 100644
--- a/toke.c
+++ b/toke.c
@@ -878,6 +878,9 @@ S_check_uni(pTHX)
     for (s = PL_last_uni; isALNUM_lazy_if(s,UTF) || *s == '-'; s++) ;
     if ((t = strchr(s, '(')) && t < PL_bufptr)
 	return;
+
+    /* XXX Things like this are just so nasty.  We shouldn't be modifying
+    source code, even if we realquick set it back. */
     if (ckWARN_d(WARN_AMBIGUOUS)){
 	const char ch = *s;
         *s = '\0';
@@ -9384,15 +9387,13 @@ STATIC char *
 S_scan_ident(pTHX_ register char *s, register const char *send, char *dest, STRLEN destlen, I32 ck_uni)
 {
     dVAR;
-    register char *d;
-    register char *e;
-    char *bracket = Nullch;
+    char *bracket = NULL;
     char funny = *s++;
+    register char *d = dest;
+    register char * const e = d + destlen + 3;    /* two-character token, ending NUL */
 
     if (isSPACE(*s))
 	s = skipspace(s);
-    d = dest;
-    e = d + destlen - 3;	/* two-character token, ending NUL */
     if (isDIGIT(*s)) {
 	while (isDIGIT(*s)) {
 	    if (d >= e)
@@ -9467,15 +9468,15 @@ S_scan_ident(pTHX_ register char *s, register const char *send, char *dest, STRL
 	if (isIDFIRST_lazy_if(d,UTF)) {
 	    d++;
 	    if (UTF) {
-		e = s;
-		while ((e < send && isALNUM_lazy_if(e,UTF)) || *e == ':') {
-		    e += UTF8SKIP(e);
-		    while (e < send && UTF8_IS_CONTINUED(*e) && is_utf8_mark((U8*)e))
-			e += UTF8SKIP(e);
+		char *end = s;
+		while ((end < send && isALNUM_lazy_if(end,UTF)) || *end == ':') {
+		    end += UTF8SKIP(end);
+		    while (end < send && UTF8_IS_CONTINUED(*end) && is_utf8_mark((U8*)end))
+			end += UTF8SKIP(end);
 		}
-		Copy(s, d, e - s, char);
-		d += e - s;
-		s = e;
+		Copy(s, d, end - s, char);
+		d += end - s;
+		s = end;
 	    }
 	    else {
 		while ((isALNUM(*s) || *s == ':') && d < e)
@@ -9563,9 +9564,10 @@ S_scan_pat(pTHX_ char *start, I32 type)
     dVAR;
     PMOP *pm;
     char *s = scan_str(start,FALSE,FALSE);
+    const char * const valid_flags = (type == OP_QR) ? "iomsx" : "iogcmsx";
 
     if (!s) {
-	char * const delimiter = skipspace(start);
+	const char * const delimiter = skipspace(start);
 	Perl_croak(aTHX_ *delimiter == '?'
 		   ? "Search pattern not terminated or ternary operator parsed as search pattern"
 		   : "Search pattern not terminated" );
@@ -9574,14 +9576,8 @@ S_scan_pat(pTHX_ char *start, I32 type)
     pm = (PMOP*)newPMOP(type, 0);
     if (PL_multi_open == '?')
 	pm->op_pmflags |= PMf_ONCE;
-    if(type == OP_QR) {
-	while (*s && strchr("iomsx", *s))
-	    pmflag(&pm->op_pmflags,*s++);
-    }
-    else {
-	while (*s && strchr("iogcmsx", *s))
-	    pmflag(&pm->op_pmflags,*s++);
-    }
+    while (*s && strchr(valid_flags, *s))
+	pmflag(&pm->op_pmflags,*s++);
     /* issue a warning if /c is specified,but /g is not */
     if ((pm->op_pmflags & PMf_CONTINUE) && !(pm->op_pmflags & PMf_GLOBAL)
 	    && ckWARN(WARN_REGEXP))
@@ -9643,12 +9639,12 @@ S_scan_subst(pTHX_ char *start)
     }
 
     if (es) {
-	SV *repl;
+	SV * const repl = newSVpvs("");
+
 	PL_sublex_info.super_bufptr = s;
 	PL_sublex_info.super_bufend = PL_bufend;
 	PL_multi_end = 0;
 	pm->op_pmflags |= PMf_EVAL;
-	repl = newSVpvs("");
 	while (es-- > 0)
 	    sv_catpv(repl, es ? "eval " : "do ");
 	sv_catpvs(repl, "{ ");
@@ -9819,8 +9815,8 @@ S_scan_heredoc(pTHX_ register char *s)
     PL_multi_open = PL_multi_close = '<';
     term = *PL_tokenbuf;
     if (PL_lex_inwhat == OP_SUBST && PL_in_eval && !PL_rsfp) {
-	char *bufptr = PL_sublex_info.super_bufptr;
-	char *bufend = PL_sublex_info.super_bufend;
+	char * const bufptr = PL_sublex_info.super_bufptr;
+	char * const bufend = PL_sublex_info.super_bufend;
 	char * const olds = s - SvCUR(herewas);
 	s = strchr(bufptr, '\n');
 	if (!s)
@@ -9892,7 +9888,7 @@ S_scan_heredoc(pTHX_ register char *s)
 	    PL_bufend[-1] = '\n';
 #endif
 	if (PERLDB_LINE && PL_curstash != PL_debstash) {
-	    SV *sv = NEWSV(88,0);
+	    SV * const sv = NEWSV(88,0);
 
 	    sv_upgrade(sv, SVt_PVMG);
 	    sv_setsv(sv,PL_linestr);
@@ -9951,13 +9947,12 @@ S_scan_inputsymbol(pTHX_ char *start)
 {
     dVAR;
     register char *s = start;		/* current position in buffer */
-    register char *d;
-    const char *e;
     char *end;
     I32 len;
 
-    d = PL_tokenbuf;			/* start of temp holding space */
-    e = PL_tokenbuf + sizeof PL_tokenbuf;	/* end of temp holding space */
+    char *d = PL_tokenbuf;					/* start of temp holding space */
+    const char * const e = PL_tokenbuf + sizeof PL_tokenbuf;	/* end of temp holding space */
+
     end = strchr(s, '\n');
     if (!end)
 	end = PL_bufend;
@@ -10003,7 +9998,7 @@ S_scan_inputsymbol(pTHX_ char *start)
     }
     else {
 	bool readline_overriden = FALSE;
-	GV *gv_readline = Nullgv;
+	GV *gv_readline;
 	GV **gvp;
     	/* we're in a filehandle read situation */
 	d = PL_tokenbuf;
@@ -10013,7 +10008,8 @@ S_scan_inputsymbol(pTHX_ char *start)
 	    Copy("ARGV",d,5,char);
 
 	/* Check whether readline() is overriden */
-	if (((gv_readline = gv_fetchpv("readline", 0, SVt_PVCV))
+	gv_readline = gv_fetchpv("readline", 0, SVt_PVCV);
+	if ((gv_readline
 		&& GvCVu(gv_readline) && GvIMPORTED_CV(gv_readline))
 		||
 		((gvp = (GV**)hv_fetch(PL_globalstash, "readline", 8, FALSE))
@@ -10032,16 +10028,16 @@ S_scan_inputsymbol(pTHX_ char *start)
 	    */
 	    if ((tmp = pad_findmy(d)) != NOT_IN_PAD) {
 		if (PAD_COMPNAME_FLAGS(tmp) & SVpad_OUR) {
-		    HV *stash = PAD_COMPNAME_OURSTASH(tmp);
-		    HEK *stashname = HvNAME_HEK(stash);
-		    SV *sym = sv_2mortal(newSVhek(stashname));
+		    HV * const stash = PAD_COMPNAME_OURSTASH(tmp);
+		    HEK * const stashname = HvNAME_HEK(stash);
+		    SV * const sym = sv_2mortal(newSVhek(stashname));
 		    sv_catpvs(sym, "::");
 		    sv_catpv(sym, d+1);
 		    d = SvPVX(sym);
 		    goto intro_sym;
 		}
 		else {
-		    OP *o = newOP(OP_PADSV, 0);
+		    OP * const o = newOP(OP_PADSV, 0);
 		    o->op_targ = tmp;
 		    PL_lex_op = readline_overriden
 			? (OP*)newUNOP(OP_ENTERSUB, OPf_STACKED,
@@ -10077,7 +10073,7 @@ intro_sym:
 	/* If it's none of the above, it must be a literal filehandle
 	   (<Foo::BAR> or <FOO>) so build a simple readline OP */
 	else {
-	    GV *gv = gv_fetchpv(d, GV_ADD, SVt_PVIO);
+	    GV * const gv = gv_fetchpv(d, GV_ADD, SVt_PVIO);
 	    PL_lex_op = readline_overriden
 		? (OP*)newUNOP(OP_ENTERSUB, OPf_STACKED,
 			append_elem(OP_LIST,
@@ -10200,8 +10196,8 @@ S_scan_str(pTHX_ char *start, int keep_quoted, int keep_delims)
 		int offset = s - SvPVX_const(PL_linestr);
 		const bool found = sv_cat_decode(sv, PL_encoding, PL_linestr,
 					   &offset, (char*)termstr, termlen);
-		const char *ns = SvPVX_const(PL_linestr) + offset;
-		char *svlast = SvEND(sv) - 1;
+		const char * const ns = SvPVX_const(PL_linestr) + offset;
+		char * const svlast = SvEND(sv) - 1;
 
 		for (; s < ns; s++) {
 		    if (*s == '\n' && !PL_rsfp)
@@ -10767,7 +10763,7 @@ Perl_scan_num(pTHX_ const char *start, YYSTYPE* lvalp)
 
 	if (!floatit) {
     	    UV uv;
-            int flags = grok_number (PL_tokenbuf, d - PL_tokenbuf, &uv);
+	    const int flags = grok_number (PL_tokenbuf, d - PL_tokenbuf, &uv);
 
             if (flags == IS_NUMBER_IN_UV) {
               if (uv <= IV_MAX)
@@ -10820,7 +10816,7 @@ S_scan_formline(pTHX_ register char *s)
     dVAR;
     register char *eol;
     register char *t;
-    SV *stuff = newSVpvs("");
+    SV * const stuff = newSVpvs("");
     bool needargs = FALSE;
     bool eofmt = FALSE;
 
@@ -10924,7 +10920,7 @@ Perl_start_subparse(pTHX_ I32 is_format, U32 flags)
 {
     dVAR;
     const I32 oldsavestack_ix = PL_savestack_ix;
-    CV* outsidecv = PL_compcv;
+    CV* const outsidecv = PL_compcv;
 
     if (PL_compcv) {
 	assert(SvTYPE(PL_compcv) == SVt_PVCV);
@@ -11014,7 +11010,7 @@ Perl_yyerror(pTHX_ const char *s)
 	    where = "within string";
     }
     else {
-	SV *where_sv = sv_2mortal(newSVpvs("next char "));
+	SV * const where_sv = sv_2mortal(newSVpvs("next char "));
 	if (yychar < 32)
 	    Perl_sv_catpvf(aTHX_ where_sv, "^%c", toCTRL(yychar));
 	else if (isPRINT_LC(yychar))
diff --git a/uconfig.sh b/uconfig.sh
index af4ce9a95c..af4c2974eb 100755
--- a/uconfig.sh
+++ b/uconfig.sh
@@ -47,6 +47,8 @@ d_attribute_noreturn='undef'
 d_attribute_pure='undef'
 d_attribute_unused='undef'
 d_attribute_warn_unused_result='undef'
+d_builtin_expect='undef'
+d_builtin_choose_expr='undef'
 d_bcmp='undef'
 d_bcopy='undef'
 d_bsd='undef'
diff --git a/util.c b/util.c
index 48cc63a253..c503dda272 100644
--- a/util.c
+++ b/util.c
@@ -929,7 +929,7 @@ S_mess_alloc(pTHX)
     Newxz(any, 1, XPVMG);
     SvFLAGS(sv) = SVt_PVMG;
     SvANY(sv) = (void*)any;
-    SvPV_set(sv, 0);
+    SvPV_set(sv, NULL);
     SvREFCNT(sv) = 1 << 30; /* practically infinite */
     PL_mess_sv = sv;
     return sv;